1. Field of the Invention
The present invention relates to a semiconductor device in which a semiconductor element is held. In particular, the present invention relates to a leadless type resin sealed semiconductor device and a manufacturing method for the same.
2. Description of the Related Art
In a conventional semiconductor device, in particular, a leadless type resin sealed semiconductor, a semiconductor element is mounted on a surface of a printed circuit board made of glass epoxy, ceramic, or the like. Further, the conventional semiconductor device has such a terminal structure that electrodes formed on the semiconductor element and a plurality of connecting electrodes formed on the surface of the printed circuit board are electrically connected to each other by metal wires, and external connecting terminals formed on a back surface of the printed circuit board and the respective connecting electrodes are electrically connected to each other via a conductive material disposed in a through-hole. Then, the surroundings of the semiconductor element are sealed with an insulating resin or the like, thereby constructing the semiconductor device.
Besides, there is given a semiconductor device, which is constructed through the following processes, in which: instead of using the printed circuit board made of glass epoxy, ceramic, or the like, a metal is electro-deposited on a conductive board to form a metal layer for mounting a semiconductor element and an electrode layer independently from each other on the board; after the semiconductor element is mounted on the metal layer, electrodes formed on the semiconductor element and the electrode layer are electrically connected to each other; the surroundings of the semiconductor element formed on the board is sealed with an insulating resin layer; and the board is peeled and removed from a resin sealing body to thereby obtain a sealing body in which respective back surfaces of the metal layer and the electrode layer are exposed (for example, refer to JP 2002-9196 A (FIGS. 2 and 10)).
However, the semiconductor device of this type (JP 2002-9196 A (FIG. 10)) has such a structure that a base board such as a printed circuited board or a ceramic board is incorporated in the semiconductor device, thereby being as thick as a thickness of the board due to its structure, and causing a problem of hindering an attainment of thinning of the semiconductor device. Moreover, in the printed circuit board, heat generated during the operation of the semiconductor elements easily tends to accumulate in the circuit board itself, thereby having a drawback of being inferior in heat dissipation property.
Besides, in the semiconductor device (JP 2002-9196 A FIG. 2), when external connecting electrodes are formed, there is employed a method involving peeling off and removing the bonding between a resin sealing body and the board, thereby exposing the electro-deposition layer made of a conductive metal. As a result, the electro-deposition layer becomes thin, and a bonding area between the electro-deposition layer and an insulating resin becomes smaller. Further, when peeling off the board, the electro-deposition layer is pulled by the board. Consequently, a terminal strength is lowered, and a problem arises, such as lowering of manufacturing yields or lowering in reliability after being mounted onto the print circuit board.